三峡水库总磷时空变化特征及滞留效应分析

磷是水域重要的营养或污染物质之一,主要随河川径流循环,河流大型水库建设和运行将对磷的输运和转化产生重要影响.基于三峡水库2008～2016年实测水文和水质资料,建立了总磷(TP)通量和泥沙通量的统计模型,利用模型插补TP的日过程浓度后建立了TP通量计算公式,分析了三峡水库TP浓度时空变化特征、通量变化及滞留效应.结果表明,不考虑区间小支流TP入汇影响, 2008～2012年,三峡入库TP浓度年际变化为0.196～0.290mg·L~(-1),年内TP浓度变化趋势呈"M"型,具有明显的双峰特性,三峡干流上游至下游TP浓度基本表现为沿程减小,部分年份清溪场断面TP浓度高于寸滩,该时段三峡年均入库TP通量和滞留率分别为8.23万t和49.76%. 2013～2016年,三峡年均入库TP通量和滞留率明显减小,分别为4.79万t和12.03%.

Tempo-spatial and Retention Analysis of Total Phosphorus in the Three Gorges Reservoir

Phosphorus, as a limiting and vital macronutrient in water, circulates mainly with sediment through rivers. The construction and operation of large reservoirs can have a profound impact on the characteristics of phosphorus transportation and transformation. Based on measured hydrological and water quality data during 2008-2016 in the Three Gorges Reservoir (TGR), a statistical model of total phosphorus (TP) flux and sediment load in different periods was established. The formula of TP flux was established by analyzing the interpolation of unmeasured TP concentration, tempo-spatial characteristics, flux variation, and the retention effect of TP in the TGR. The results indicated that taking no account of the effects of TP inflows of tributaries, annual TP concentration in the TGR varied between 0.196 mg·L^-1 and 0.290 mg·L^-1 during 2008-2012, and inner-annual changes in TP concentration presented an "M" type with two obvious peaks. TP concentration decreased slowly from upstream to downstream of the TGR, and increased significantly from Cuntan to Qingxichang in some years. The average annual TP flux and retention rate of the TGR were 82300 t and 49.76% during 2008-2012, respectively. During 2013-2016, the average annual TP flux and retention rate decreased significantly, to about 47900 t and 12.03%, respectively.